The present invention relates generally to improvements in managing battery power consumption in mobile telephones. In particular, the invention relates to advantageous methods and apparatus for establishing an operational state that consumes significantly less power than the standby state of a typical mobile telephone, yet provides the capability to rapidly resume a normal operational state.
The rapid growth of the mobile telephone industry has resulted in millions of users of handheld, battery powered mobile telephones. Many users of such mobile telephones leave their telephones switched off unless they need to make an outgoing call, thereby conserving the unit""s battery power for days, or even weeks. An increasing number of users, however, leave their telephones switched on all of the time so that they can receive incoming calls throughout the day and night. Most handheld mobile telephones have sufficient battery power to remain in standby mode for a period of hours; or as long as a day. As mobile telephone technology has advanced, newer models ha,e. decreased in size substantially, while still incorporating more features and functions that consume more battery power. One result of these technological advances is that the telephone""s internal battery now typically occupies half, or more, of the total physical volume of the telephone, and may account for the majority of the unit""s total weight. At the same time, the desire for longer operational time periods between battery recharge cycles has increased. Although new battery technologies, such as lithium-ion, are now supplanting the once ubiquitous nickel-cadmium, the state of the art in battery technology has not kept pace with consumer demand for longer life batteries.
A typical handheld mobile telephone can be manually switched on or off by use of a physical power switch. While switched off, the telephone battery may still supply a nominal amount of power to maintain a user""s customizable features, such as telephone number lists, and the like. The power output capability of a mobile telephone battery typically degrades slowly over time due to a number of factors. Such factors include the hysteresis effect associated with recharging nickel-cadmium (Ni-Cad) batteries and internal leakage currents, and these factors may be accelerated by environmental conditions such as high storage temperatures, humidity, and the like.
When a mobile telephone is switched on, the unit must perform a power-up sequence that establishes a radio frequency (RF) link with an appropriate base station. Upon completion of this sequence, the telephone is in a standby mode of operation and is ready for use. The telephone""s radio receiver actively monitors the signals from the nearest, or other appropriate, base station to determine if there are any incoming calls for the mobile telephone user. The base station alerts the mobile telephone to incoming calls by broadcasting the telephone""s mobile identification number (MIN). The MIN is the same as the user""s mobile telephone number, and is used to identify the mobile telephone unit to the mobile telephone network. If the MIN is being broadcast, the telephone responds by activating a ringer, or the like. If the subscriber answers the incoming call, the telephone switches to active mode, and the call is completed in full duplex operation. In full duplex, the telephone is simultaneously receiving and transmitting RF signals, and therefore consuming battery power at a very high rate. Upon completing a telephone call, the unit resumes standby mode operation, and is ready to initiate or accept another call. If the user switches the mobile telephone off to conserve battery power, the telephone may transmit a power-off signal to the base station. This signal can be utilized by the mobile telephone network to conserve RF bandwidth by not broadcasting the MINs of mobile telephones that the network has identified as being switched off.
Existing techniques for extending mobile telephone battery life include reducing the internal clock cycling of the telephone microprocessor, entering a sleep mode if the telephone is inactive for a predetermined period of time, utilizing more efficient radio amplifiers, and utilizing software algorithms that reduce the radio signal output level when the telephone user is listening, but not speaking, during a mobile telephone call. The methods and apparatus of the present invention. His described further below, can provide extended battery life when used alone or in combination with these existing techniques.
The present invention recognizes that a need exists in a variety of contexts for techniques to extend the effective operational time period between battery recharge cycles, irrespective of the particular battery technology utilized.
One embodiment of the present invention incorporates special circuitry and software into the design of a. standard mobile telephone unit. This circuitry and software sense the first radio frequency (RF) signal signifying an incoming call, and utilize that signal to rapidly switch the telephone into a normal operational state, thereby allowing a user to receive an incoming call. One implementation of this embodiment incorporates this special circuitry into a power control subsystem device that is incorporated into the design of a standard mobile telephone. This power control subsystem device may be incorporated into an integrated circuit (IC), an application specific integrated circuit (ASIC), or a digital signal processor (DSP). In another implementation of the present invention, this device may comprise a low power microprocessor, such as a Microchip PIC 12C509, and other components.
The power control subsystem device enables the mobile telephone to function as if the unit is in standby mode, while consuming significantly less power than such a mobile telephone ordinarily would in standby mode. In operation, the device monitors the appropriate radio frequencies to detect the mobile telephone""s MIN, while the telephone""s baseband microprocessor remains powered off. This mode of operation is known as idle mode. Since a mobile telephone baseband microprocessor must operate at a high clock frequency to provide real-time voice communications, it consumes a relatively large amount of power even when in standby mode. Since the device of the present invention provides very limited functionality, such as detecting the telephone""s MIN and switching the baseband microprocessor on and off, it may operate at a relatively low clock frequency, and therefore consume much less power than a baseband microprocessor in standby mode.
Upon detecting the MIN, the device instructs the telephone to enter the active mode, thereby activating a telephone""s ringer, or the like, to notify the telephone subscriber that there is an incoming call. If the subscriber chooses to answer the incoming call, the telephone remains in the active mode and operates in a normal manner. Upon completion of the telephone call, the telephone returns to the standby mode to await another call. The device may be programmed to return to the idle mode after a fixed period of time, or after a user selected period of time. The device may also be programmed to allow the telephone user to manually switch the telephone to idle mode. The device may incorporate a dedicated memory device, or it may utilize a portion of the telephone""s memory. The memory is utilized to store the information that enables the telephone to rapidly resume an active operational state. Typically, when a mobile telephone is switched on, the unit must perform a power-on sequence whereby internal system checks, are performed, speed dialing numbers are loaded, and the like. The telephone then performs a registration process wherein the RF interface is established, a nearby base station is identified, the appropriate base station is located, RF channels are allocated and the telephone subscriber""s MIN is broadcast. In one embodiment of the present invention, the memory device retains this registration information. When the telephone detects an incoming call, the stored registration information is supplied immediately to the telephone baseband microprocessor, thereby significantly reducing the time period required for initialization of the telephone.
In another embodiment of the present invention, the mobile telephone registration information is stored in a database at a mobile switching center (MSC) that is collocated with the base station. Typically, when a mobile telephone is switched off, it sends a signal to the MSC indicating that the telephone is being switched off. This allows the MSC to signal the mobile telephone network that the mobile telephone is not capable of terminating calls. This arrangement allows the mobile telephone network to notify the caller immediately, and eliminates the need to broadcast the mobile telephone""s MIN over the network. In this embodiment of the present invention, a signal is sent to the MSC when the mobile telephone enters idle mode. This allows the MSC to store the mobile telephone user""s registration information, and to signal the mobile network that the mobile telephone is in idle mode. Thereafter, if the MSC receives an incoming call from the public telephone network, the MSC checks to see if the called MIN is in its database. If so, then the MSC transmits the registration information to the mobile telephone. The mobile telephone enters standby mode upon detecting it""s MIN. The mobile telephone receives the registration information from the MSC, thereby allowing the mobile telephone to rapidly resume active mode, and answer the incoming call. Storing the registration information in the MSC allows the device described above to operate without a dedicated memory for storing registration information within the mobile telephone.